I am unable to preview any game play in blender
The engine is set to Blender internal. As of 2.73 P only starts the game engine when the render engine is set to Blender Game at the top of the screen:



Also note that that file was made in 2.4x. The 2.4x python api is not compatible with the 2.5x+ api, so the python scripts won't work. If you want to run that file, you can download 2.49b here.